^  LIBRARY 

CIRCULAR    NO.  4.9.    SECOND   SERIES.  STATE    PLANT    BOARD 

j      United  States  Department  of  Agriculture, 

y  DIVISION    OF    ENTOMOLOGY, 

\  A 

^  L.  O.  HOWARD.  Entomoloeist. 

THE   SILVER   FISH. 

{Lepisma  saccharina  Linn.) 

By  C.  L.  Marlatt, 

First  Assistant  Entomologist. 

[Revised  reprint  from  Bulletin  No.  4,  New  Series.  Division  of  Entomology,  U.  S.  Department  of 

Agriculture,  pp.  76-78.] 

This  insect  (fig.  1)  is  often  one  of  the  most  troublesome  enemies  of 
books,  papers,  card  labels  in  museums,  and  starched  clothing,  and 
occasionally  of  stored  food  substances.  Its  peculiar  fish-like  form  and 
scaly,  glistening  body,  together  with  its 
very  rapid  movements  and  active  efforts 
at  concealment  whenever  it  is  uncovered, 
have  attached  considerable  popular  in- 
terest to  it  and  have  resulted  in  its  re- 
ceiving a  number  of  more  or  less  descrip- 
tive popular  names,  such  as  silver  fish, 
silver  louse,  silver  witch,  sugar  fish,  etc. 
The  species  named  above  is  the  common 
one  in  England,  but  also  occurs  in  this 
country,  and  like  most  other  'domestic 
insects,  is  now  practically  cosmopolitan. 
It  has  a  number  of  near  allies,  which 
closely  resemble  it,  both  in  appearance 
and  habits.  One  of  these  (Lepisma 
[ThermoMa]  domestica  Pack.)  has  cer- 
tain peculiarities  of  habit  which  will  be 
referred  to  later.  The  peculiar  appear- 
ance of  the  common  silver  fish  early 
drew  attention  to  it,  and  a  fairly  accu- 
rate description  of  it,  given  in  a  little  work  published  in  London  in 
1665  by  the  Royal  Society,  is  interesting  enough  to  reproduce : 

It  is  a  very  small,  silvery,  shining  worm  or  moth  which  I  found  much  con- 
versant among  books  and  papers,  and  is  supposed  to  be  that  which  corrodes  and 
eats  holes  through  the  leaves  and  covers.  It  appears  to  the  naked  eye  a  small, 
glittering,  pearl-colored  moth,  which  upon  the  removing  of  books  and  papers 
in  the  summer,  is  often  observed  very  nimbly  to  scud  and  pack  away  to  some 
lurking  cranny  where  it  may  better  protect  itself  from  any  appearing  dangers, 
life  head  appears  big  and  blunt,  and  its  body  tapers  from  it  toward  the  tail, 
smaller  and  smaller,  being  shaped  almost  hke  a  carret.i 


Fig. 


1.— Lepisma    saccharina , 
enlarged  (original). 


adult- 


Micrographia,  R.  Hooke,  London,  1665. 


2 


On  account  of  its  always  shunning  the  light  and  its  ability  to  run 
very  rapidly  to  places  of  concealment,  it  is  not  often  seen  and  is  most 
difficult  to  capture,  and  being  clothed  with  smooth,  glistening  scales, 
it  will  slip  from  between  the  fingers  and  is  almost  impossible  to  secure 
without  crushing  or  damaging.  It  is  one  of  the  most  serious  pests  in 
libraries,  particularly  to  the  binding  of  books,  and  will  frequently  eat 
oS  the  gold  lettering  to  get  at  the  paste  beneath,  or,  as  reported  by 
Mr.  P.  R.  Uhler,  of  Baltimore,  often  gnaws  off  white  slips  glued  on 
the    backs    of    books.      Heavily   glazed   paper    seems    very   attractive 

to  this  insect,  and  it 
has  frequently  hap- 
pened that  the  labels 
in  museum  collections 
have  been  disfigured 
or  destroyed  by  it,  the 
glazed  surface  having 
been  entirely  eaten 
off.  In  some  cases 
books  printed  on  hea- 
vily sized  paper  will 
have  the  surface  of 
the  leaves  a  good  deal 
scraped,  leaving  only 
the  portions  covered 
by  the  ink.  It  will 
also  eat  any  starched 
clothing,  linen,  or  cur- 
tains, and  has  been 
known  to  do  very  se- 
rious damage  to  silks 
which  had  probably 
been  stiffened  w  i  t  h 
sizing.  Its  damage  in 
houses,  in  addition  to 
its  injury  to  books, 
consists  in  causing  the  wall  paper  to  scale  off  by  its  feeding  on  the 
starch  paste.  It  occasionally  gets  into  vegetable  drugs  or  similar 
material  left  undisturbed  for  long  periods.  It  is  reported  also  to  eat 
occasionally  into  carpets  and  plush-covered  furniture,  but  this  is  open 
to  question. 

The  silver  fish  belongs  to  the  lowest  order  of  insects — the  Thysa- 
nura — is  wingless,  and  of  ver}^  simple  structure.  It  is  a  worm-like 
insect  about  one-third  of  an  inch  in  length,  tapering  from  near  the  head 
to  the  extremity  of  the  body.  The  head  carries  two  prominent  antennae, 
and  at  the  tip  of  the  body  are  three  long,  bristle-shaped  appendages, 

AG CA 


T 
Fid.  2.— Lepismadomestica:  Adult  female— enlarged  (original). 


one  pointing  directly  backward  and  the  other  two  extending  out  at  a 
considerable  angle.  The  entire  surface  of  the  body  is  covered  with  very 
minute  scales  like  those  of  a  moth.  Six  legs  spring  from  the  thorax, 
and,  while  not  very  long,  they  are  powerful  and  enable  the  insect  to  run 
with  great  rapidity. 

In  certain  peculiarities  of  structure,  and  also  in  their  habits,  these 
anomalous  insects  much  remind  one  of  roaches,  and  their  quick,  gliding 
movements  and  flattened  bodies  greatly  heighten  this  resemblance. 
More  striking  than  all,  however,  is  the  remarkable  development  of  the 
coxae  or  basal  joints  of  the  legs  in  the  silver  fish,  which  finds  its  coun- 
terpart in  roaches,  and,  taken  in  connection  with  the  other  features  of 
resemblance,  seems  to  point  to  a  very  close  alliance  between  the  two 
groups,  if,  indeed,  the  silver  fish  are  not  merely  structurally  degraded 
forms  of  roaches  and  to  be  properly  classed  with  the  Blattida. 

Another  of  the  common  silver  fishes  of  this  country,  referred  to  in  the 
opening  paragraph,  has  developed  a  novel  habit  of  frequenting  ovens  and 
fireplaces,  and  seemingly  revels  in  an  amount  of  heat  which  would  be 
fatal  to  most  other  insects.  It  disports  itself  in  numbers  about  the 
openings  of  ranges  and  over  the  hot  bricks  and  metal,  manifesting  a 
most  surprising  immunity  from  the  effects  of  high  temperature.  This 
heat-loving  or  bakehouse  species  (fig.  33)  was  described  in  1873  as 
Lepisma  domestica  by  Packard,  who  reported  it  to  be  common  about 
fireplaces  at  Salem,  Mass.  This  species  is  also  very  abundant  in  Wash- 
ington. What  is  evidently  this  same  insect  has  become  very  common, 
particularly  in  the  last  year  or  two,  in  England  and  on  the  Continent, 
where  it  manifests  the  same  liking  for  hot  places  exhibited  by  it  in  this 
country.  The  habit  of  this  species  of  congregating  in  bakehouses  and 
dwellings,  about  fireplaces  and  ovens,  has  given  rise  to  the  common 
appellation  for  it  in  England  of  "  fire-brat."  Similar  descriptive  names 
are  applied  to  it  also  on  the  Continent.  This  species  closely  resembles 
the  common  silver  fish  in  size  and  general  appearance,  but  may  be 
readily  distinguished  from  it  by  the  presence  on  the  upper  surface  of 
dusky  markings.  It  also  possesses  well-marked  structural  differences, 
which  have  led  to  its  late  reference  to  a  distinct  genus — Thermobia. 
An  Italian  entomologist,  Rovelli,  has  described  this  insect  under  the 
descriptive  name  furnorum,  from  its  inhabiting  ovens,  and  the  name  of 
the  genus  to  which  it  is  now  assigned  by  English  entomologists  is  also 
descriptive  of  its  heat-loving  character.  A  Dutch  entomologist,  Oude- 
mans,  reports  that  he  has  found  it  in  abundance  in  all  bakehouses  that 
he  has  examined  in  Amsterdam,  where  it  is  well  known  to  bakers  and 
has  received  a  number  of  familiar  names. 

REMEDIES. 

Advantage  may  be  taken  of  the  liking  of  these  insects  for  fabrics  and 
other  articles  containing  starch  to  poison  them  by  slipping  into  all  the 

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UNIVERSITY  OF  FLORIDA 


3  1262  09228  3588 

crevices  where  they  occur — in  bookshelves  and  backs  of  mantels,  under 
washboards,  and  in  the  bottoms  of  drawers — bits  of  cardboard  on  which 
a  thick  boiled  starch  paste  liberally  poisoned  with  arsenic  has  been 
spread  and  dried.  One  of  our  correspondents  reports  complete  relief 
by  this  measure.  The  silver  fish  readily  succumbs  to  pyrethrum,  and 
wherever  this  can  be  applied,  as  on  bookshelves,  it  furnishes  one  of  the 
best  means  of  control.  For  starched  clothing  and  similar  objects  liable 
to  be  injured  by  it,  frequent  handling  and  airing  and  the  destruction  by 
hand  of  all  specimens  discovered  is  to  be  recommended,  in  addition 
to  the  poisoned  cardboard  remedy.  Little  damage  is  liable  to  occur  in 
houses  except  in  comparatively  moist  situations  or  where  stored  objects 
remain  undisturbed  for  a  year  or  more. 

Washington,  D.  C,  June  20,  1902. 

O 

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